This invention relates to apparatus for inflating tires, and more particularly, to apparatus for inflating tires quickly, controllably and accurately prior to testing the tires on a tire testing machine.
Prior to testing tires in a uniformity machine or the like, the tires must be raised to a preselected pressure. It is desirable that each tire of a kind be tested at the same pressure as every other tire being tested. Bringing the tire to the desired pressure must be done as quickly as possible.
Apparatus currently in use includes a shop supply of air and a regulated supply of air with conduit connecting those supplies to the tire. A valve is provided to connect the shop supply to the tire to raise the pressure in the tire to the level, well above the test pressure, required to seat the tire bead on the test rim. The valve is then shifted to the exhaust position to exhaust the air from the tire down to that which is close to the regulated pressure. The valve then shifts to the pressure regulator which may either exhaust or introduce air to the tire in order to bring it to the test pressure. The known apparatus is imprecise and is not fully automatic, requiring manual adjustment of pressure set points with visual observation of gauges and the like. The pressure regulator has been an analog device that is manually set. More specifically, with a manual pressure regulator, the operator manually adjusts a spring force operating on a diaphragm.
An objective of the present invention has been to provide apparatus to inflate the tire quickly and precisely to the desired pressure.
Another objective of the invention has been to provide such inflation apparatus wherein all operations are performed automatically with automatic compensation in succeeding tires for errors in the test pressure in the preceding tires.
Another objective of the invention has been to provide apparatus which permits the inflation pressures to be controlled digitally rather than being adjusted using analog regulators.
The objectives of the invention are attained by providing an automatic controller connected to the valve system which shifts among "shop pressure," "exhaust" and "regulated pressure." The controller has provision for digitally setting the bead seat and test pressures to desired levels. A sensor monitors the level of pressure in each tire. A valve shifts the connections to the tire among the shop pressure, the exhaust and the regulated pressure to seat the tire beads on the test rim first, the exhaust from that high bead seat pressure and then to regulate to the test pressure.
When the operator starts the test, the shop supply is introduced to the tire which rapidly inflates the tire to the bead seat pressure. Prior to reaching the bead seat pressure, the controller energizes the appropriate solenoid to shift the valve system to exhaust, anticipating the time delay occasioned by the solenoid operation of the valve. Thus, after energizing the solenoid, the pressure continues to be introduced into the tire until the bead seat level is attained at about which time the valve system completes its shift to exhaust. The presure is then exhausted until it is close to the test pressure level. At that time the controller shifts to pressure regulated air, again anticipating a delay in the solenoid operation time. When the shift is completed, it is preferred that the level of air in the tire be below the preset test level. Air through the pressure regulator brings the pressure up to about the level for the test.
That final pressure is compared by the controller to the desired test pressure. The difference between the two pressures is stored in the controller and this difference is added to an accumulative error signal so that the voltage output to the electrical pressure controller or pressure regulator is corrected to provide more accurate inflation of each successive tire. Usually by the time of inflation of the third tire in the sequence, the desired test pressure is achieved and remains constant in successive tires.
The advantages of the invention include: the digitally settable bead seat and test pressures; the anticipation of solenoid reaction time; and the closed loop control of pressure which specifically allows a less accurate voltage-to-pressure transducer and which does not require adjusting during each tire's cycle.
The several objectives and features of the present invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawing which is a combined air and electrical circuit diaphragm of the system of the present invention.